How was human sacrifice a part of life throughout the pre-columbian americans?

Human sacrifice, a feature of all Meso-American and Andean religions, has often given rise to the portrayal of the American civilizations as particularly cruel and backward, and it has to be admitted that the practice is so alien to our way of thinking that an objective assessment is very difficult. Accounts on the extent of the practice vary widely. Without doubt the largest number of human sacrificial offerings were made by the Aztecs. Berdan (1982) quotes reports on the dedication of the great dual temple in Tenochtitlán in 1487 that range from 80,400 captives sacrificed over a four day period (according to a Spanish account) to 20,000 in the Codex Telleriano-Remensis (an Aztec manuscript). Even if these figures represent an extreme event, regular monthly or fortnightly human sacrifice was practiced by the Aztecs, the Incas, the Mayas and others. It has to be understood that human sacrifice was accepted as part of everyday life, that everyone was a potential candidate for sacrifice, and that it was considered an honour when fate determined one's death on the altar. Some wars between the Aztecs and the neighbouring Tlaxcallans and Huexotzincos were fought periodically by mutual agreement with the sole purpose to obtain prisoners of war for future sacrifice.

The answer is crop yield.